Immersion tube type furnace



G. J. HALES Immsron TUBE TYPE FURNACE Filed April 12 Feb. 11, 1936.

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Patented Feb. 1l, 1936 UNITED STATES amsn xoN'rUna'rm muses George J.Halealtoekyliver, Ohio, allgnor'to General Electric Company, acorporation of New York Medion Alirll 12, 1934, No. 120,194

4 Claims. .(Cl. 26S-8) This invention relates to furnaces, moreparticularly to electric furnaces for carrying out certain heat treatingoperations for metals, such as and the like, and it has for its objectthe provision of an improved furnace of this character which is moreefficient in its operation and which'is more durable than thoseheretofore known. This invention has particular application to Dfurnaces for treating wire, rods. tubesand like forms of metals, such asribbonl sheets, etc.. wherein the furnace charge. that is, the materialto be treated, is supplied to andpassed through the furnace. Certainfurnaces of this 5 type heretofore known comprise a relatively elongatedtube, constituting a treating chamber, in

which a suitable selected atmosphere, such as.'

hydrogen, is maintained. This tube is provided with a heating `zonewherein the `material is g heated to the treating temperature and acooling sone wherein the material is cooled before.

it is withdrawn from the furnace. The heating zone is usually heated bymeans of electric heating elements arranged on the exterior of 5thetubeinaheating chamberthatsurroundsor envelops the heating zone. Y

These furnaces have, in the main, been quiteA satisfactory. but aresubject to certain disadvantages.' The heat distribution in the heatingporo tion of the tube is not always uniform and consequently thetemperature throughout this zone may vary. It may vhappens.therefore,that the metal being treated will not be heated uniformly as it throughthe furnace.l Moreoven it l5 has been found that an uneven distributionof the heat in the tube at'the heating zone tends to warp the tube outof shape., This invention contemplates the provision of improved meansfor heating the furnace, where- Lo by heat is uniformly distributed overthe heating acne so as to insure a uniform temperature conditionthroughout the zone. This assures a uniformly heated product, andmoreover, pregts warping of the tube due to uneven heat- Ls In additionto this, this invention contemplates the provision of a furnace which ismuch quicker in its operation-than those heretofore generally known,whereby the output bf treated i metal is materially increased. I'

In accordance with this invention, the heating zone of the furnaceisheated-by a mass of heated material, preferably in the liquid state,which has a high heat storage capacity and a is relatively high thermalconductivity. This mass tions of the zone throughout its length. The

tubular heating zone is, thusuniformly heated to the same temperaturethroughout so that the successive Alengths of material being treatedwill be uniformly heated as they pass through the heating zone. l0

Theheating medium may be of any suitable material having a relativelyhigh heat conductivity and thermal capacity, such as' lead, aluminum,copper. mercury. etc. 'I'he heating medium may be heated conveniently ina suitable metal melting tank or crucible in which the heating zone ofthe treating tubeis located.

For a more complete'understanding of this invention, reference should behad to the accompanying drawing in which Fig. l. is a fragmentaryvertical sectional view of an electric metal melting furnace arranged inaccordance with this invention: Fig. 2 is a fragmentary plan view of theelectric furnace shown in Fig. l. portions being shown in section andportions being broken away so as to illustrate certain details ofconstruction: Fig. 3 is a fragmentary vertical sectional view of anelectric furnace of modified form arranged in accordance withmy-invention; and Pig. 4 isa atic view illustrating so temperaturecontrol means used .in my fur- Referring more particularly to Figs. land 2. I have shown my invention in'one form as applied to anelectrically heated metal annealing furnace comprising a plurality ofmetallic tubes Il, each of which forms an elongated treating chamber.The tubes I! have identically the same construction. Each treating tubeIl comprises a heating-zone il and a cooling zene I2. The 40 coolingzone I2 is surrounded by a iacket through which a cooling fluid, such aswater.

lmaybecirvmlatedbymeansofaninletpipeIl and an outlet pipe it; Thisjacket, as shown,

fimctions'to cool all -of the tubes I0. y 45 The heating zone Il of eachtube Il is heated uniformly throughout its entire length'by means of amass Il of a suitable heat transfer medium completely enveloping .theouter surface of the portion Il. As previously pointed out. 5o

this heat transfer medium preferably will be formed of a metal having arelatively high thermal capacity'l and heat conductivity. such as lead,aluminum, copper, mercury. etc.

It iscontemplated'that this heat transfer medium I8 will be heatedsumciently to bring it to the liquid state so that all portions of theheating chamber II will be completely covered by and in intimate thermalcontact with the heat transfer medium. whereby all parts of the heatingY bottom walls of the receptacle. As shown, the

receptacle I1 rests upon the bottom wall of the outer lining I8. Thisouter lining may be formed of any suitable material, such as suitableheat refractory bricks. The. receptacle is provided at its top with aperipheral ange 20 upon which restsv a suitable cover 2l made of anysuitable heat refractory material.

The metal transfer medium I6 may be heated in any suitable manner, butwhere relatively low temperatures are required in the heating zone I I..

it is preferable to employ immersion heating elements of the sheathedtype for this purpose, such as disclosed in the U. S. patent to C. C.Abbott, No. `1,380,718, dated August 14, 1928. As shown a plurality ofelectrical immersion heaters 22 of this type are supported in. theinterior of the receptacle I 1. Each of the heaters 22 has a suitableresistance element embedded in refractory insulating material andsurrounded by a metallic sheath, which is cast in a mass of 'a suitablemetal. 'nie leads 28 of the resistance element are passed through aninsulating tube 24 and outlet box 26 and may be connected to anysuitable source of electrical supply. It will be understood that anysuitable number of these elements may be used.

' As shown, I have provided eight of the elements,

` crucible and that portion of the tubethat enters two in each side andend wall of the crucible.

Each of the heating elements 22 has anupper horizontal arm 22a whichissecured to the refractorylining llby meansofbolts22bsoasto support theheating element 22 in the receptacle I1. These elements may be, andoftentimes preferablywillbe-securedtotherlmoriiangeof the crucible.Preferably, the walls of the crucible will rise somewhatA above thewalls I8. asclearly shown in. Fig. 1, and preferably, the upperprotruding portions of the crucible walls will be provided with notchesor cut away portions 2C to receive the -arm portions 22a that rest uponthe walls I8. Byreason of this construction, the cover member 2i can lieflush on the flange 28 at the top of the receptacle.

It will be observed that the heating portion I I of each tube i8 issupported within the crucible above its bottom wall so thatl the heattransfer Vmedium I6 can completely envelop the tube.

'lhe tube III where it passes out of the crucible, that is, where itjoins into the cooling zone I2 has a fluid-tight joint 21 with the wallof the crucible. This joint may be formed by welding. or otherwisesubstantially integrally uniting the walls of the tube with the metallicwalls of the crucible.

A nula-tight. seal is also provided between the the crucible so as toprovide for thermal expansion of the tube within the crucible. 'I'hisseal comprisesatubesurroundingthehibe Ilon the exterior of the crucibleat the entrance end of the heating zone II and communicating with thecrucible, as clearly shown in Fig. l. This tubular member has afluid-tight Joint 8l with the adjacent' wall of the crucible. This jointalso 'may be formed by welding or otherwise integrally uniting thetubular member with the crucible wall. The outer end of the tube isclosed by a suitable cover member 3| which is welded or otherwisesecured to the tube with a fluid-tight joint 32. 'I'he cover is providedwith a centrally arranged aperture through which the tubular member I0 Aseparate tube 2l may be provided for each tube Il, or a single tube 28may be provided for all `of the tubes I8.

It will be observed in view of the foregoing arrangement that the liquidtransfer medium within the crucible can iiow into the tube 28 so as tocompletely slnround the portion of the tubular l treating chamber I0 onthe exterior of the crucible immediately next to the crucible. Thetubular member 28 will have a diameter suillciently large to provide arelatively thick layer of the heat transfer medium about the tubularmember III.

The tube 28 is cooled' by means of a suitable cooling medium u so thatthe layer of heat .transfer medium surrounding the tubular member vI0will be solidified. As shown', the tubeis cooled bymeansofasmtablecoolingjacketuthrough which the cooling uid 38. which may bewater, is circulated by means of an inlet pipe 8i and an outlet pilleItwillbe'obrvedthatbyreasonofthisarrangement, the frozen or solidiedmetal forms itsownseal. Thissealwillpermitunequaiexpension between thetubular treating tube I8 and the cmeible andv thereby prevent warping ofthe tube. 'Ihisisbecause thetube Ilwillmoverelativetothesealingmasssoastoprovideforunequal movements of thetube Il and the crucible walls due to thermal expansion. If desired, themetalsurrmxndingthetubellmaybecoveredso as to4 put partially solidifyit.-v

A suitably selected or controlled medium, such as hydrogen, isVmaintained in the heating and coolingzonesil and I2.Thismediumissupplied to each of the furnace tubes I8 through an inletpipe l1 which communicates with the tube substantially at the junctureoi the heating and cooling zones. The medium entering at this pointdividesandowsinoppomtedirectionsthroughthe heating and cooling zones.Preferably a common supply manifold 38 for the various supply tubes 31will be provided.

It will be understood that in the operation ofthefurnacathematerialtobetreatedwillbe passed through the furnacetreating chambers Il-iirst through the heating zone II and thenthroughthecoolingzone'. Itwill alsobeun derstood that the material inthrough the heating zone will be heated to the treating temperature,while maintained inthe selected atmosphereinthiszone.andwillbepassedthrough the cooling zone I2 where it willV be cooled submtially to roomtemperature, while in the selected atmosphere, before the ma is passedout from the furnace.

The heating elements 22 are controlled to maintain a constant operatingtemperature in 1 the bath Il. Any suitable temperature controlmeansmaybeusedforthispurpe. InFig. 4. I have shown in quite ditlc formone means for controlling the heating elements 22 to hold a constanttemperature in the bath Il.:

'I'he relay is energized fromv the source 42 and its energization iscontrolled by a suitable temperature responsive element Il immersed inthe metal IB so as to respond to its temperature, as shown in Figs. land 2. It will be understood that the device 4I will be arranged tocontrol the energization of the relay I3 to energize the contacter Il toapply the heat when the temperature of the metal I6 falls below apredetermined value, whereas when the temperature of the metal II risesabove the predetermined value it will operate the relay to deenergizethe contactor 4I so as to shut of! theheat.

It is to be noted that I have provided means for uniformly heating theheating zone Il throughout its length. 'I'he relatively large mass I6 ofheat transfer medium having a relatively large storage capacity providesa large reservoir of heat which is available at all times. And moreover,by reason of the fact that the transfer medium I8 has a relatively highheat conductivity, heat will be transferred from the me- .dium It to theheating chamber Il at a very rapid rate, the rate. of course. dependingupon the thermal capacity and the heat conductivity of the particulartransfer medium. If lead be used. the transfer is six times or more asrapid as if the tube Ii were heated in the furnaces heretofore generallyused. It is possible. therefore, to pass the material being treatedthrough the furnace at a considerably greater speed than has beenpossible heretofore.

Moreover, not'only is the output of my furnace increased, but it has amore uniform quality because all. portions' of the material passedthrough the furnace are heated uniformly to the-treating temperature inthe heating zone.

Another advantage of my furnace is that there is considerably lesswarpage of the tubular members l0. because they are evenly and uniformlyheated throughout the entire length of the heating'zone. f

If higher temperatures are desired it is preferable to use thearrangement shown in`Fig. 3.A In this arrangement the heat treatingtubes 5U are arranged in substantially the same fashion as are the tubesi0, that is, they are provided with a heating zone and a cooling zone52. The heating zone is heated by a'heat transfer medium 53 which isheated to a liquid state in a suitable crucible 5l. The crucible Il isarranged in substantially the same fashion as the crucible of thefurnace of Figs. l and 2. The crucible in Fig. 3, however, is not heatedby immersion heating elements, but by relatively high temperatureresistance-heating elements 5. TheseV resistors preferably consist of atribbons of a suitable heat resistance material. such as anickel-chromium alloy, which are'hung in a series of loops on suitablesupports, such as refractory hangers 56 secured in the side walls ofsaid insulating outer lining BI.A Suitable terminals 58 for the heatingresistors are brought out through the lining B1. Similar resistors 59may be positioned 4 beneath the bottom wall of the crucible. The

heating means for this furnace likewise will be provided with suitabletemperature control means arranged so that a constant temperature isheld in the bath il.

The remainder of the construction of the furnace of this form isidentically the s ame as the form shown in Figs. i and 2, and thefurnace operates in substantially the same fashion.

It is preferable to heat the transfer medium to the liquid state. Itwill be understood, however, that the medium, after it has once beenheated and allowed to cool to the solid state. mayv then subsequently beused in the solldcondition to transfer heat to the tube I0. The liquidstate, however, is more desirable.

While I have shown particular embodiments of my invention, it will beunderstood, of course,

that I do not wish to be limited thereto since many-modifications may bemade.` and I, lthere-- fore, contemplate by the appended claims to coverany such modications as fall within the true spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. A continuous process annealing furnace l wherein the material beingannealed is passed through the furnace comprising a crucible, anelongated metallic tubular metal member forming a treating chamberhaving a portion constituting a heating zone passing through saidcrucible above its bottom wall, a heat transfer medium having arelatively high heat conductivity and thermal capacity within saidcrucible, means for applying heat to said medium' to liquefy it wherebyit envelops said heating zone touniformly heat it throughout its length,means providing a fluid impervious joint between said tube ,at one endof the heating zone and the wall of said crucible where said tube passesout of said crucible, and means for cooling a portion ofthe heattransfer medium at the other end of said heating zone to solidify saidmedium and thereby seal said tube at said outer end of said zone.

2. A metal treating furnace comprising a crucible, an elongated metallictubular member forming a treating chamber having a portion yconstitutinga heating zone within said crucible above its bottom wall passingthrough the opposite walls of said crucible, a metallic heat transfermedium having a relatively high heat capacity and thermal conductivitywithin said crucible, means for applying heat to said transfer medium toliquefy it whereby it envelops the portion of said tube forming saidheating z one to uniformly heat it. throughout its length, a fluid-tightjoint between said tubular member at the exit end of said heating zoneand said crucible where said tubular member leaves said crucible, atubular member communicating with said crucible at .the entrance end ofsaid heating zone and surrounding a portion of the length of saidtubular member on the exterior of said crucible so that said portion issurrounded by a layer of said heat transfer medium, and means forbringing a cooling medium into thermal relation with said tubular memberso as to solidify said layer of transfer 3. A continuous process furnacecomprising a crucible containing a heat transfer medium, means forheating said medium to liquefy the same, a treating tube extendingthrough said crucible and immersed in said medium, means forming a jointimpervious to said medium between one side of said crucible and saidtube and a joint between another side of said crucible and said tubecomprising a cooled and solidified portion of said medium.

4` A continuous prooefurnaee comprising e. crucible containing enormally solid heat trans- Ier medium. means for heating said medium toliquefy the same, a treating tube extending 5 through said crucible andimmersed in said medium, and means forming e joint impervious to saidmedium between one side oi said crucible and said tube,v said crucibiehaving an outward extension at the opposite side thereof through GEQRGEJ. HALEB. t

